(CBS/AP) On Sept. 13, 2001, Ahmed Fathy Mehalba applied for a job as a gate security guard at Logan International Airport, where two days earlier a pair of jets had been hijacked and flown into the World Trade Center towers.

Mehalba was back in Boston Monday, when he was arrested at Logan after authorities found classified information in his possession, federal officials said. The 31-year-old Egyptian-American was a translator at the U.S. prison for terror suspects at Guantanamo Bay, Cuba.

The arrest was the third involving someone who worked closely with the largely Muslim, non-English-speaking population of about 660 suspected terrorist fighters being held at Guantanamo. The two other men, another translator and a Muslim chaplain, are both in the military.

Mehalba is a civilian who formerly served in the Army and twice started but failed to complete a military intelligence course to become an interrogator, two defense officials said on condition of anonymity.

He was medically discharged from the Army in May 2001 and later hired by a private defense contractor to be a translator at the Guantanamo Bay prison, they said.

Officials said they had no further information on why he didn't complete the courses, nor what the medical discharge was for.

Jose Juves, a spokesman for the Massachusetts Port Authority, which runs Logan Airport, said Mehalba was never considered for the guard position for which he applied.

He received a form letter rejecting his application, said Juves, who had no further information on why Mehalba was not considered for the job. Gate guards perform a variety of duties, including guarding access to airfields and access to the airport.

Juves also said Mehalba was a Boston cab driver who had two Logan taxi pool violations, for operating without his hackney license and failing to report to a designated area.

Mehalba's application for a Massachusetts hackney license, dated March 3, 2003, lists a post office box in Salem as his address. Under "Current Employer," he says he is a Department of Defense contractor. A message left at the telephone number on the application was not returned.

Dennis Murphy, a spokesman for the Department of Homeland Security, said Mehalba is a naturalized U.S. citizen originally from Egypt who had flown Monday to Boston from Cairo, with a stop in Milan, Italy.

He was taken into custody after Immigration and Customs Enforcement officials spotted what appeared to be classified material.

Mehalba was carrying 132 compact discs, which he said contained only music and videos, according to a government affidavit filed in court. But agents checked his bags and found at least one that appeared to contain unspecified classified information, some of it marked "SECRET," the affidavit said.

He denied knowing how the information got on the disc, saying he bought the discs in Guantanamo "as blanks," the affidavit said.

At a brief hearing Tuesday in U.S. District Court in Boston, Mehalba entered no plea and was detained pending a probable cause hearing scheduled for Oct. 8. On the charge of making false statements, he faces up to five years in prison and a fine of up to $250,000.

Mehalba, wearing jeans and an orange golf shirt, said nothing during the hearing, except to tell the judge that he could not afford his own attorney.

Michael Andrews, the court-appointed attorney who represented Mehalba at Tuesday's hearing, said, "He intends to vigorously defend himself against these charges."

The arrest of a second translator raised new concern about how the military had checked the dozens of translators needed to help with interrogations of al Qaeda and Taliban suspects whose native languages include Arabic, Pashto, Dari and Uighur.

Officials said they had been watching Mehalba and that still others were being investigated. A new assessment team traveled to the prison this week to study procedures and make recommendations on security, defense officials said.

Defense Department officials said Mehalba worked at Guantanamo for San Diego-based defense contractor Titan Corp. Titan spokesman Wil Williams confirmed that Mehalba worked for the firm but said he was on leave when the arrest occurred.

Last week, authorities said an Air Force enlisted man, Ahmad I. al-Halabi, had been charged with espionage in July, accused of sending classified information about the Guantanamo facility to an unspecified "enemy." He also was accused of planning to give other secrets about the prison to someone traveling to Syria.He has said he is innocent.

CBS News Correspondent Jim Stewartreports federal investigators found evidence that Al-Halabi had unique access to the cells of many of the 660 suspected al Qaeda and Taliban prisoners. It is not known what access Mehalba had although detainees were usually accompanied by an interpreter during interrogations and administrative procedures.

The other man in custody is Army Capt. Yousef Yee, a Muslim chaplain who is being detained without charge at the Navy brig in Charleston, S.C. Al-Halabi is behind bars at Vandenberg Air Force Base, Calif.

Officials at Guantanamo said last week that they had strengthened security at the prison in the wake of the arrests, including making certain that restrictions on handling documents, making phone calls and sending e-mails were being followed.

Officials have not commented on whether they think any of those detained or being investigated may have compromised interrogations at the facility. Dozens of translators have been employed at the prison, where the main work has been to question suspects for any information they may have on terrorist networks and especially to collect information that might prevent future attacks.